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The purpose of this paper is to compare four life data models, namely the exponential and the Weibull models, and their corresponding generalized versions, q-exponential and q-Weibull models, by means of one practical application.

Application of the models to a practical example (a welding station), with estimation of parameters by the use of the least squares method, and the Akaike Information Criterion (AIC).

The data of the example considered in this paper is divided into three regimes, decreasing, constant and increasing failure rate, and the q-Weibull model describes the bathtub curve displayed by the data with a single set of parameters.

The simplicity and flexibility of the q-Weibull model may be very useful for practitioners of reliability analysis, and its benefits surpasses the inconvenience of the additional parameter, as AIC shows.

The q-Weibull model is compared in detail with other three models, through the analysis of one example that clearly exhibits a bathtub curve, and it is shown that it can describe the whole time range with a single set of parameters.

The purpose of this paper is to analyze mathematical aspects of the q‐Weibull model and explore the influence of the parameter q.

The paper uses analytical developments with graph illustrations and an application to a practical example.

The q‐Weibull distribution function is able to reproduce the bathtub shape curve for the failure rate function with a single set of parameters. Moments of the distribution are also presented.

The generalized q‐Weibull distribution unifies various possible descriptions for the failure rate function: monotonically decreasing, monotonically increasing, unimodal and U‐shaped (bathtub) curves. It recovers the usual Weibull distribution as a particular case. It represents a unification of models usually found in reliability analysis. Q‐Weibull model has its inspiration in nonextensive statistics, used to describe complex systems with long‐range interactions and/or long‐term memory. This theoretical background may help the understanding of the underlying mechanisms for failure events in engineering problems.

Q‐Weibull model has already been introduced in the literature, but it was not realized that it is able to reproduce a bathtub curve using a unique set of parameters. The paper brings a mapping of the parameters, showing the range of the parameters that should be used for each type of curve.

Several studies focus on agri-food value chain from a consumer or from a supply chain perspective. But there is little investigation integrating both approaches and providing empirical evidence from developing countries. The purpose of this paper is twofold: first, it describes the supply chain of organic products in Brazil, which is an emerging market. It describes how retailers manage its supply chain (wholesalers and small producers) in an organic own brand of fresh products. Second, this paper identifies the motivations, attitudes, beliefs and personal values behind Brazilian consumers' decision to purchase organic food.

Qualitative and quantitative techniques were used in two stages. First, it presents a case study of the organic supply chain. Then, a survey carried out with 261 consumers at supermarkets in a Brazilian city is presented.

The case study points out that retailers transfer to wholesalers the responsibility to manage small organic producers. It also suggests that as the organic product is under the retailer own brand, and therefore most of the value perceived by the consumer is retained by the retailer. Survey results indicate that organic consumers have strong individual values and benefits are the most significant predictors of attitude toward organic food for the Brazilian consumers interviewed. Availability is significantly related to the intent to purchase organic food, which is a key point for the supply chain to respond efficiently to consumers' demand.

This paper is based on a single case study and the survey is applied in only one city of Brazil.

The study contributes to expand the value analysis through a combination of quantitative and qualitative techniques, including consumer behaviour and supply chain management in the same analysis. It also adds to the debate on value, proposing Schwartz Value Theory as a complementary approach to value analysis.